Generally OK although I've had some poor balsa. The design is also much older. Don't expect the same kind of tab/lock design as in a Sig, or others. Generally it's "carve the balsa to shape" or cut the sheet, glue and sand, sand, sand. As an example the fuselage bulkheads on the Killer Kaos are not pre-formed. You cut the supplied balsa stick to construct the bulkheads. The nose ahead of the firewall is a few large pieces of balsa that you carve and sand to shape. It's nothing really hard, but not like the nice laser cut stuff you may be used to. Also the fuselages tend to be on the narrow side.